/**
 * @author ghp
 * @title 爬楼梯
 */
class Solution {
    public int climbStairs(int n) {
        int p=0, q=0, r=1;
        for (int i = 1; i <= n; i++) {
            p = q;
            q = r;
            r = p+q;
        }
        return r;
    }

}